This invention relates to power supplies and, more particularly, to a power supply including a high frequency resonant converter having current shunting means.
The present invention will be described in association with an uninterruptable power supply (UPS) system as the invention was developed for such use, however, it is to be understood that the invention is not limited to such use. The invention may be used in other power supply systems utilizing resonant converters as will become evident hereinafter.
It may be explained here that high frequency series resonant converters are normally operated near their resonant frequency in order to deliver maximum power to the load in the output circuit to which they are connected. Furthermore, such series resonant converters have an operating frequency which varies directly with the loading of the output circuit. A the loading of the output circuit decreases, the operating frequency of the converter will drop and may result in the operating frequency falling within the audible frequency range, e.g., 16 to 20,000 Hz. UPS systems typically operate over a wide load range. Consequently, a UPS system employing a high frequency series resonant converter, absent correction, may exhibit objectional audible noise at lighter power levels.